you're probably splitting hairs here. If you want to try something new in terms of taste, go for substance WPI in watermelon, its great. Grape was good too, i havent tried the other flavors.
You can buy it from a sponsor too:
Substance WPI (2 lb) By PrimaForce
In terms of whey, i highly doubt you're going to notice huge differences between two similar products. Even WPI vs WPC is pretty close, IMHO. For this reason i just always use Dymatize Elite - its cheap and tastes really good. Caffe Mocha and Mint Chocolate are by far my favorites I've ever tried:
Elite Whey 5 lb (5 lb) By Dymatize
I've used AllTheWhey and really liked not only their product, but also their customer service. I just find it more convenient to buy all my products from one retailer, rather than making separate protein purchases